Wednesday, December 19, 2007

So, finally this semester is over. I gotta say it was no easy ride but things seem to have gone good.

Some time ago I posted about teaching at a ranked university and I had high expectations about it. Although I expected more, I have to admit things went much better here. Students seemed more interested (not totally, but more) and one thing that really surprised me was that they were grateful to me for teaching them. I got a lot of thank you's for doing such a good job and for making it fun. This is a first, no student had thanked or congratulated me for the way I thought them. It feels good, and I think that is the main difference between the students here and the students at my old university: they appreciate their education and don't necessarily take it for granted.

I found, however, a problem with the grading. There is a lot of subjectivity when transforming a number into a letter. I feel all the grades I gave are appropriate to the student's work/abilities but they don't always feel that way. Two or three people told me they think they deserve a better grade because their lab partner got a letter higher than them. That makes no sense to me: Give me a better grade because he/she worked harder or knows more than me. But then again, who's right? I guess I'll never find out.

Anyways... let's wait for next semester. Will it be even better? Happy Holidays!

Friday, November 2, 2007

It has been a long journey to discover neutrinos, not only from the experimental point of view but also from the theoretical standpoint. All of it started when Pauli proposed the existence of a new charge-neutral, massless, weakly interacting new particle to explain energy conservation in beta decay (radioactive process). You can immediately see the trouble with that particle: it is undetectable... almost. People started thinking about possible ways to measure the neutrino and sources of them. It turns out the sun makes millions and millions of them so they now look at those neutrinos.

The problem in question is not a simple one and the experiment requires a lot of engineering work. The "detector" consist of a large volume of heavy water, though water can also be used. How much water? About 1000 tons of it. But this is not the end of the story, to make matters worse, it needs to be underground ~1.5-2 miles below the ground to shield it from the cosmic radiation which also makes a count in the detector. Then, it has to be all clean, pure water, no dirt or dust, etc. which sounds easy but underground is kind of not clean right? Now, it comes the detection part: they detect something called Cherenkov radiation (produced when a charged particle, say an electron, travels faster than light inside an insulating medium) using photomultipliers, something like 9500 at SNO. The problem here is that many things make a photomultiplier detect a count, I think at SNO they got something like half a billion counts but only about 3000 were possibly neutrinos, which means that once you have "data" you have to sort it out into probabilities of it being a neutrino. This task takes more than a year of work.

They initial prediction include three neutrinos, one for each lepton (electron, muon, tau). We now know that they do come in three (named 1,2,3), but not directly the ones initially thought of. There are three quantum-mechanical wave functions that superpose (they combine) to form something like the classical "beats" with sound waves. The superposition of those give rise to the other three. Also, they do have a mass but a minuscule one. This particular property forced physicist to reformulate the most of the neutrino theory, since the massless condition implies certain theoretical results, namely that neutrinos cannot change flavor.

There are many experiments taking place or being planned to extend the research in neutrino physics, specially for those coming directly from the sun. If you are interested check out the wikipedia entry, it has links to the different underground labs and to the professors and universities where they work. Some of them have explicit adds for grad and/or undergrad students.

Friday, October 12, 2007

Recently, I learned about something really cool called Whistlers. It is a low frequency electromagnetic wave (audio range) produce by lighting striking the ionosphere. After the lightning strikes, an electromagnetic pulse is created and it travels very long distances. Due to dispersion, the higher frequencies of the pulse travel faster and with the proper equipment you can receive them and actually hear the sound of a whistle. It turns out these signals can come from "half around the world". Wow.

Wednesday, October 3, 2007

So I know this guy very successful (as far as I can tell) in his line of work though it has nothing to do with science, it has to do with business, finance, etc. I have to be honest, I have asked him for advice when it comes to money and I have been satisfied with his answers.

Recently, however, I have been able to see him in everyday action and it is pretty disappointing his level of stupidity when he is presented with physical situations that require a little common sense. Or course I am not talking about building a car, or a space shuttle, nor understading quantum mechanics or something like that. I am talking about simple things like untying a knot or putting together one of those pieces of furniture that come in a box with instructions that I thought even a kid could do without much trouble, etc, etc, etc.

I am the type of guy that believes non-science or non-engineering majors shouldn't take any science course, what for? Eventually they will go on to work in something that has nothing to do with science (most likely) and they could use those credit hours to learn more about their fields. On top of that, any one that has TA'd a science lab for non-science majors will tell you that 99.9% of those students do not give a fuck about the material they're suppose to be learning. I still maintain that opinion, I think that serves no real purpose, and I don't care what universities say about their broad curriculum or anything like that. Bottom line: if you are not in science/engineering you will not know/remember any of the things you were suppose to learn in your sciences courses.

I still have a problem with people being stupid when it comes to obvious physics. Specially those ones that think they are soooo smart because they have a good salary in some business-oriented job. I am not saying there are no smart people in business or finance, I am just saying some of those think they are smarter than everybody else just because their paycheck is larger than the average scientist's salary. Where did that come from? Did they learn that in college? Who told them the size of the paycheck makes them smart automatically?

Thursday, September 13, 2007

Some time ago I posted a comment about how photosyntesis shows quantum mechanics charateristics in the macroscale.

Well, there are apparently only 3 biological processes that show quantum mechanical behavior in the large scale. Photosynthesis as already mentioned is one of them, but also vision by absorbing discrete lumps of energy and converting them into an electrical current, and pulmonary activity which I don't completely understand why.

Who would have thought only 3 uh? In any case, nature is so cool that didn't forget to add "macroscopic" QM systems in our bodies!

On a different note, I am realizing how difficult it is to maintain an updated blog. I'll try to be better at it.

Thursday, September 6, 2007

Next week begins the lab for which I'll be the TA. It is an undergraduate electromagnetism lab for engineers. I am excited about it. Although this is not the first time I teach, I am looking forward to it because I am now at a well ranked university. There are rumors about it being much more fun. I hope the stories are true.

I enjoy physics, but I enjoy teaching physics a lot more. I've had good students before, even if just a small number of them. We'll see how this goes.

I just read a very interesting article. It is not new, but it is to me. It talks about how out society has pushed college education into making a grade, and thus, "making" some students beg for a better grade at the end of the semester, when there is nothing more to do.

Friday, August 17, 2007

I just got the August 2007 issue of Physics Today and found something interesting to talk about.

On page 19, an article titled "Electric fields have potential as cancer treatment" talks about how common physics can be used in alternate fields, such as medicine and biology. Cancer is characterized by an uncontrolled production of cells, that is, the regulating mechanism for cell division stops working and therefore cells are produced in large quantities. Existing cancer treatments hamper cell division, but unfortunately they attack healthy cells too. Although the article discusses a model for Electric fields to work as cancer treatment, the final answer has yet to be known.

Whatever the answer is, this article shows how an understanding of the physical properties of biological entities can lead to the use of well known physics to contribute in new developments. For those thinking about biophysics, that is a great area to work in.

Thursday, July 19, 2007

Some people do not appreciate the practical importance of Quantum Mechanics, considering it nothing more than some calculations and ideas in the pages of a book. Of course, the man-created digital electronics era would not be possible without an understanding of QM but also, as it turns out, certain everyday natural phenomena are possible due to the quantum characteristics of our world. One these natural phenomena is plant photosynthesis.

That interesting way plants use to convert sunlight into their fuel wouldn't be possible without the quantum-mechanical properties of the world. The main idea is very similar to what happens in photoabsorption of semiconductors, in which a photon of the right energy excites an electron into the conduction band. However, the multiple excitations and availability of states makes the process complicated. This is just another example of how simple models (energy and forbidden bands) have implication in many different fields and/or situations.

Photosynthetic processes have a nearly 100% efficiency. So, if we can ever control/mimic the way plants do photosynthesis we'll have, to name one example, highly efficient solar fuel cells.

For the mean time, we'll have to keep admiring nature and its quantum mechanical ways!

The idea is actually pretty good. They post a new question every week, and "give" you one week to figure it out. The cool part of it is that they complement the questions by adding pictures or videos. Then, they publish the answer a week later including more videos or pictures as "proof" so that no doubt remains!!!

The website is maintained by the Physics Department at the University of Maryland,.... if you guys are reading: good work! keep it up!!!